You have seen the threat of John Strake to slay Arnold Aylmer by black magic. You have seen Arnold Aylmer slay John Strake by white magic. You see Arnold Aylmer alive and talking to you now. And yet you don't believe it."

"No, I do not believe it," said Father Brown, and rose from his chair like one terminating a visit.

"Why not?" asked the other.

The priest only lifted his voice a little, but it sounded in every corner of the room like a bell. "Because you are not Arnold Aylmer," he said. "I know who you are. Your name is John Strake; and you have murdered the last of the brothers, who is lying outside in the snow."

A ring of white showed round the iris of the other man's eyes; he seemed to be making, with bursting eyeballs, a last effort to mesmerize and master his companion. Then he made a sudden movement sideways; and even as he did so the door behind him opened and a big detective in plain clothes put one hand quietly on his shoulder. The other hand hung down, but it held a revolver. The man looked wildly round, and saw plain-clothes men in all corners of the quiet room.

That evening Father Brown had another and longer conversation with Dr. Boyne about the tragedy of the Aylmer family. By that time there was no longer any doubt of the central fact of the case, for John Strake had confessed his identity